I. Field of the Invention
This invention relates to an electronic system with a composite substrate which is composed of a circuit board mounted on a lead frame.
II. Description of the Prior Art
FIG. 1 shows a prior art U.S. Pat. No. 6,212,086, it discloses a DC-to-DC converter system which includes a copper clad 110 on bottom for equal heat distribution. The prior art also includes a circuit board 120 mounted on the top surface of the copper clad 110. Electronic components including main transformer 130, output inductor 140, synchronous rectifiers 150, output capacitors 160, and input capacitors 170 are all mounted on the circuit boards 120. A discrete output connector is connected to the circuit board 120 through a flexible circuit board in the right side of the package.
However, one of the main disadvantages is that the circuit board 120 is not a good heat conductor for transferring the heat generated from the electronic components 120, 130, 140, 150, 160, and 170 downward to the copper clad 110. A circuit board is good for circuitry arrangement capability but not good for heat distribution for heat generating electronic components; while in contrast, a copper clad is good for heat distribution but not good for circuitry arrangement as compared to a circuit board. Persons skilled in the art have been striving for developing a substrate which displays both advantages—larger circuitry arrangement capability and good heat distribution capability.